This application is related to Japanese Patent Application No. 2001-034109 filed in Feb. 9, 2001, whose priority is claimed under 35 USC xc2xa7119, the disclosure of which is incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a duplexer device and particularly a duplexer device using a surface acoustic wave filter.
2. Description of the Related Art
Recently, a mobile phone and a mobile information terminal have been quickly spread with development of mobile communication systems and have been demanded to have a small size and high performance.
The radio frequency in use covers wide bands, for example, from 800 MHz to 1 GHz bands and from 1.5 to 2.0 GHz bands.
In the recent development of a mobile phone, terminals have been developed to have high functionality, for example, a dual mode (e.g., a combination of an analog mode and a digital mode, or a combination of digital modes, i.e., a TDMA (time division multiple access) mode and a CDMA (code division multiple access) mode and a dual band (e.g., a combination of an 800 MHz band and a 1.9 GHz band, or a combination of a 900 MHz band and a 1.8 GHz band or a 1.5 GHz band).
Along with the trend, parts used in a mobile phone (such as a filter) are also demanded to have high functionality. In addition to the demand of high functionality, a small size and a low production cost are also demanded.
The mobile communication apparatus utilizes an antenna duplexer in an RF section branching and generating signals transmitted and received through an antenna.
FIG. 36 is a block diagram showing a radio frequency section of conventionally used mobile phone.
An audio signal 100 inputs from a microphone are converted to a modulated signal of the modulation system of the mobile phone system by a modulator 101 and then converted to a designated carrier frequency by a local oscillator 108. Thereafter, the signal passes through an interstage filter 102, which selects only a signal having the prescribed transmission frequency, and then amplified to a desired signal intensity by a power amplifier 103, and transmitted to an antenna duplexer 105. The antenna duplexer 105 transmits only the signals of the designated transmission frequency to an antenna 104, and the antenna 104 transmits the signal as a radio signal into the air.
On the other hand, a signal received by the antenna 104 is transmitted to the antenna duplexer 105 to select only a signal of a designated frequency. The selected signal is amplified by a low-noise amplifier 106 and transmitted to an IF filter 110 through an interstage filter 107, and only a message signal is selected by the IF filter 110. The signal is transmitted to a demodulator 111 and taken out as an audio signal 100. The antenna duplexer 105 is positioned between the antenna 104 and the so-called audio signal processing circuit and has such a function that the transmission signal and the reception signal are distributed to prevent interference of them.
The antenna duplexer necessarily has at least a transmission filter and a reception filter, and in order to prevent interference of the transmission signal and the reception signal, it also has a matching circuit, which is also referred to as a phase matching circuit or a line pattern for phase matching.
The antenna duplexer for a highly functional terminal includes a complex duplexer with a dielectric material or a surface acoustic wave filter using a dielectric material on at least one part, and a constitution containing only-a surface acoustic wave filter. A duplexer using a dielectric material has a large size and is difficult to make a mobile terminal small and thin.
Even the case using a surface acoustic wave duplexer on one part, the size of the dielectric material device prevents a mobile terminal from having a small and thin size.
A conventional duplexer using a surface acoustic wave filter includes a module type comprising a printed circuit board carrying separate filters and a matching circuit, and a one-piece type comprising filter chips for transmission and reception mounted in a multi-layer ceramic package and a matching circuit provided inside the package.
The duplexer of these types can be reduced in volume by a ratio of about from 1/3 to 1/15 and in height by a ratio of about from 1/2 to 1/3 in comparison to the duplexer using a dielectric material. The cost of the duplexer can be equivalent to the dielectric material device by using the surface acoustic wave device and reducing the size of the device.
In order to cope with the demand for further reduction in size, which will arise in future, it is necessary to use the structure using a multi-layer ceramics package described in Japanese Unexamined Patent Publication No. Hei 10(1998)-126213 and is also necessary to form two filters on one chip and to apply a flip chip mounting technique using no wire connection. In any case, two components, i.e., a duplexer package capable of being airtightly sealed, which carries two surface acoustic filters, and a matching circuit for constituting the duplexer with the two filters, are necessary.
The matching circuit is formed by arranging a line pattern having a prescribed length in one layer in a package having a multi-layer structure.
In order to satisfy the demanded characteristics as a duplexer and to cope with the demand of reduction in the size of the duplexer package, the arrangement of the line pattern of the matching circuit is necessarily considered.
Particularly, in the case where the line pattern and external connection terminals (wire bonding pads) of a duplexer package are arranged closely, there is a problem in that sufficient isolation cannot be ensured, and the depression characteristics outside the pass bands of the two. surface acoustic filters constituting the duplexer are deteriorated.
The invention is duplexer device in that isolation between a line pattern of a matching circuit and signal terminals of a duplexer package is sufficiently ensured, so as to stabilize the characteristics of the duplexer.
The invention relates to a duplexer device comprising two surface acoustic wave filters having band center frequencies different from each other and a line pattern for matching phases of the two surface acoustic wave filters, wherein provided are: a wire bonding pad layer having a plurality of pads including pads for connecting the line pattern with terminals on the surface acoustic wave filters and pads for connecting a common terminal connected to an external antenna with the line pattern; and a first pad connecting one of the surface acoustic. wave filters and a first end of the line pattern and a second pad connecting the common terminal and a second end of the line pattern being arranged at positions that are the most distant from each other inside the wire bonding pad layer.
The invention also relates to a duplexer device comprising two surface acoustic wave filters having band center frequencies different from each other and a line pattern for matching phases of the two surface acoustic wave filters, wherein provided are: a wire bonding pad layer having a plurality of pads including pads for connecting the line pattern with terminals on the surface acoustic wave filters and pads for connecting a common terminal connected to an external antenna with the line pattern; a line pattern layer located below the wire bonding pad layer, the line pattern layer having the line pattern; and an external connection terminal layer located below the line pattern layer, the external connection terminal layer having an external connection terminal for connecting the surface acoustic wave filters with an external circuit, the line pattern layer being formed so that a distance dS between a point in the line pattern layer, at which a path connecting the terminal on the surface acoustic wave filter with the external connection terminal intersects the line pattern layer, and an arbitrary point on the line pattern is set to a prescribed value or more.
According to the invention, a duplexer device of a small size stabilizing the depression characteristics of the counterpart can be provided.